如何从 MapDB 中批量读取记录,而不是一次全部读取?
我有一个通过 MapDB 保存在磁盘上的 1,000 条记录的列表。
private fun storeRecordsInFile(records : List<Record>): String {
val fileName = "/some/location/temp_file.db"
val db = DBMaker.fileDB(fileName).fileMmapEnable().closeOnJvmShutdown().make()
val diskBasedRecordsList = db.indexTreeList("recordsList").create()
records.forEach { diskBasedRecordsList.add(it) }
db.commit()
db.close()
return fileName
}
我能够一次阅读所有这些记录。
private fun readRecordsFromFile(fileName: String): List<Record> {
val db = DBMaker.fileDB(fileName).fileMmapEnable().make()
val diskBasedRecordsList = db.indexTreeList("recordsList").open()
//read from disk based list
val recordsList = mutableListOf<Record>()
val size = diskBasedRecordsList.size
for(i in 0 until size-1){
recordsList.add(diskBasedRecordsList[i] as Record)
}
db.close()
return recordsList
}
但是,我想在内存中一次仅读取 100 个块/批次(即不一次获取内存中的全部 1000 条记录)?